10 Tips on Greenhouse Temperature Control for Gardeners

10 Tips on Greenhouse Temperature Control for Gardeners

Fluctuating temperatures are the bane of any grower's life. Nothing kills plants faster than plummeting thermometers or scorching sunbeams.

Whether indirectly or not, most problems we see in plants are caused by environmental stress. Temperature can affect everything from germination to flowering and even the quality of your crops.

If you're trying to maintain a climate-controlled greenhouse and have been finding it challenging, you've come to the right place. Keep reading to find out everything you need to know about greenhouse temperature control and why it could make or break your yield.

Why Is It Essential to Manage the Temperature of Your Greenhouse?

When temperatures fall outside of a crop's preferred range, vital biological processes like photosynthesis can stall or stop altogether. Growers will have a hard time controlling their climates if they don't have the right-sized heating and cooling systems in place.

Inaccurate measurements can add to temperature difficulties, which only makes the problem worse. By using the right tools and addressing the problems below, anyone can improve their temperature problems.

What Is the Ideal Greenhouse Temperature?

While it's difficult to say outright what the ideal temperature of your greenhouse should be, there is a base optimal range. However, it does depend on what kinds of plants you're growing.

This base range typically sits at around 80 and 85 degrees Fahrenheit (27 to 29 degrees Celsius). Maintaining the ideal temperature in your greenhouse will promote good plant performance. Good performance means healthier and more nutritious fruits and vegetables.

A greenhouse temperature that is too cold or too hot can cause stress in your plants, which can lead to mildew, mold, or pests, as well as unhealthy plants.

Temperature and Humidity Are Not Exclusive

When you change the temperature, you also change the humidity, and vice versa. Yet, while they are linked, an increased amount of one or the other can have different effects on your plants. With high levels of humidity come pests and diseases. To mitigate these effects, we must monitor and manage our systems with a firm hand.

It's not only about the air either; the plant temperature itself is also important for increased yield. Good air quality is critical to maintaining consistency across the greenhouse. When we build a greenhouse, we're essentially aiming to create a contained microclimate.

Smaller microclimates can exist within the same space and are created by small pockets of very humid, hot air. They can appear in specific places within the greenhouse or in unexpected spots; it just depends on your specific setup.

Our Tips for Greenhouse Temperature Control

Perhaps you’re searching for your ideal greenhouse humidity or trying to maintain good airflow (and struggling)? We guarantee there is something in your grow space that is stalling your process. Finding what it is can be tricky, but solving the problem? That’s the easy part.

1. Ensure Accurate Readings

The ideal place to start if you're having issues with temperature is to make sure your temperature measurements are correct. If the data you're using doesn't correspond with what's actually happening in the growing area, you can't respond and act accordingly.

To improve the accuracy of our readings, we should take measurements in multiple areas of the greenhouse or grow room. This includes taking air and soil readings, as well as plant and leaf temperatures (if you're a conscientious gardener).

To establish an average daily temperature, we should be measuring all areas as often as possible, ideally over a 24-hour period. We should set up our thermometers or sensors carefully to make sure we're getting the most precise air temperature readings. It's especially critical to keep the sensors out of direct sunlight and away from grow lights, as they can skew the accuracy of the measurement.

We should also keep sensors away from any heating or cooling equipment that could interfere with results. Ideally, sensors and thermometers should be level with the top of the plant canopy for the best temperature readings.

2. Effective Systems for Heating and Cooling Are Essential

A major component to successful year-round growth is ensuring we have properly sized our heating and cooling equipment for the location. We can start by calculating the surface area of the building, which is then used to estimate the heating requirements of a greenhouse.

Without due consideration into these areas, temperatures will be difficult to manage and your expenses will increase along with them.

The importance of a correctly sized heating system becomes more pressing in winter when additional heating is most needed. It can be difficult to determine exactly how much heating is required to sustain the correct temperatures, especially for large-scale growers.

You could always enlist the help of an industry professional, who can build a specialized heating system based on your individual needs. And, as expensive as they may be right off the bat, more efficient heating equipment will save you money and heartache in the long run.

3. Use Smart Controllers

With all the technology involved in grow room temperature regulation, it can be difficult to keep track of everything. Smart controllers provide farmers and growers an easy alternative to temperature management because they automatically regulate the growth environment.

All environmental control equipment, including heating, cooling, and ventilation systems, as well as sensors and thermometers, can be connected to a greenhouse or grow room controller. Smart controllers can also connect to computers and smartphones, allowing you to monitor your temperatures at all times.

Bringing all your controlling equipment into a single, easy-to-use interface is the ideal solution for managing large-scale grow rooms. We're looking for simplicity, as this is what's going to give us the most crop yield.

4. Ensure Your HVAC System Is Properly Sized

Sizing your greenhouse HVAC (heating, ventilation, and air conditioning) system accurately is a crucial factor in accommodating any heating and cooling loads you may have. Our aim is to get the most plant density out of each area and to do this, we need air circulation and dehumidification. 

Measure out your space and install the right equipment as needed. If it's blazing outside, you want to keep your internal climate cool, or at the very least, controlled.

5. Consider Horizontal Air Flow

Similarly, being able to efficiently cool a grow room or greenhouse, even on the warmest summer days, boosts crop development and yields. We know that taking control of air movement is one of the most effective techniques we have for controlling the temperature of the surrounding air.

Horizontal Air Flow (HAF) fans can help disperse temperatures in a more uniform way, which creates more sufficient airflow across the grow room or greenhouse.

Installing HAF Fans

Remember, we were talking about pockets of heat and mini microclimates? This is where horizontal fans are particularly useful. Within your rooms or greenhouse zones, try to avoid "dead air" zones (zones with no airflow). Fans that are too high above the plants do not provide enough airflow within the crop, but fans that are too near to the crop will hinder your ability to control moisture levels.

It's a delicate balance, and one that is going to take some trial and error, so don't be discouraged if it doesn't immediately work.

6. Incorporate Shade Curtains Into Your Greenhouse

During high-light and high-temperature months, use greenhouse shade control tools, or shade drapes. Shade curtains block 30 to 50% of light and should be closed during the day's brightest and hottest hours. If the greenhouse does not have a retractable shade curtain, we can paint whitewash over the roof to act as a shade curtain. Just be sure to wash it off when the cooler months arrive, as we don't want our plants to freeze.

You can also choose to use blackout tarps or light deprivation sheets to control the amount of light coming in.

7. Ensure Proper Ventilation

Open the doors and windows of your greenhouse during the hot summer months to allow for natural ventilation. You can also roll up the walls of a hoop house to let warm air out.

Some greenhouses have hinged roofs that open, allowing air to circulate freely. You could also opt for an open-roof greenhouse or one with sidewalls that can be readily opened as needed.

In your greenhouse, install roof and wall vents where you can, and incorporate pockets where you can vent air in a high tunnel system. Because hot air rises, it will exit via the vents above and enter through the wall vents, allowing cool, fresh air to enter. This will ensure that your green room is well ventilated.

8. Opt For a Wet Wall Method

A wet wall is a cooling system that pumps water through the wall, and a fan that cools the water that has evaporated. You'll need to keep an eye on the humidity levels if you use this strategy, as they can be prone to rising. Cut off the water supply to the wet wall as soon as the moisture in the air rises.

On a hot, sunny day, the temperature inside your greenhouse can soon soar to 100 degrees Fahrenheit, which is far from ideal. On winter evenings, the temperature within the greenhouse might equalize with the outdoor setting, resulting in a chilly atmosphere.

When the humidity in your greenhouse is too high, your plants won't be able to breathe correctly, which might lead to fungus growth. Leaves will dry out and your plants may wilt if the moisture content is too low.

9. Populate Your Greenhouse

A greenhouse full of plants produces a natural evaporative cooling effect, so fill your greenhouse up! Filling the greenhouse with as much soil and as many plants as the space allows will increase the overall thermal mass of the greenhouse.

As the thermal mass will hold in all that lovely heat overnight, your temperature management problems will be lessened. Another alternative is to put hay bales inside your grow space, which will also elevate the thermal mass.

Because hay holds so much water, it will help regulate the internal temperature of your greenhouse.

10. Use Heat Mats Where Necessary

Heat mats are ideal if you're trying to germinate or cultivate seeds and young plants. They raise the temperature of the soil, thus preventing it from getting too cold, which could kill or damage your plants.

They should be put on a level, dry surface close to a power source so we can plug them in. You can use a thermostat to set the proper temperature for your soil and then monitor and automate your heat mats to turn off or on as needed.

Build Your Greenhouse With Farm Plastic Supply

Your greenhouse will only be as efficient as the temperatures allow. Creating a climate-controlled greenhouse is of the utmost importance to keep your plants healthy and your yield plentiful.

We hope the outlined methods will provide meaningful insights for your greenhouse temperature control journey. Know that there is no problem too big or too overwhelming. If you're just getting started, why not head on over to our building supplies and accessories section to get you going?